1. Field of the Invention
This invention relates generally to gaging devices, particularly to gages for measuring diameters of non-round threaded objects.
2. Summary of the Prior Art
Precision measurement of the diameters of non-round threaded objects using hand-held micrometers, calipers, or the like can be very difficult, and yield inaccurate results. If the object to be measured becomes canted between the jaws or measuring points of a micrometer, the measurement can be inaccurate. Furthermore, a hand-held micrometer must be screwed closed to obtain a measurement. Overtightening of the micrometer can damage the object to be measured, and the degree of tightness can vary between measurements, rendering the measurements less accurate. Various solutions to this difficulty have been proposed in the prior art.
U.S. Pat. No. 1,499,730, Jul. 1, 1924, to Hanson discloses a micrometer body mounted to a frame provided with a V-block for measurement of threaded objects such as fluted taps. U.S. Pat. No. 2,332,229, Oct. 19, 1943 to Jelley discloses a V-block anvil to be attached to a micrometer body for measuring the diameter of threaded members. U.S. Pat. No. 2,521,428, Sep. 5, 1950, to Vizuete discloses another V-block anvil attachment for a micrometer, also for measuring diameters of threaded members. U.S. Pat. No. 2,557,073, Jun. 19, 1951, to Hanson discloses yet another V-block anvil for attachment to a micrometer body, for measurement of diameters of threaded objects. U.S. Pat. No. 4,947,327, Dec. 4, 1990, to a common inventor discloses a roller gage for measuring diameters of cylindrical threaded objects.
All of these prior art gages simplify the measurement of the diameters of generally cylindrical threaded objects by eliminating the need to carefully place the object to be measured within the jaws, or measuring points, of a micrometer. However, these prior art gages are not particularly adapted for measurement of non-round threaded objects, such as fluted taps and thread-rolling screws. Non-round threaded objects are particularly susceptible to misalignment in the jaws of a caliper or micrometer. Furthermore, the prior art gages are incapable of giving a measurement reading directly from the micrometer scale of the diameter that is measured. Further, these prior art gages require the use of a multiplying factor to convert the micrometer scale reading into an actual diametrical measurement.
The requirement of a multiplying factor complicates the use of these prior-art gages. Such complication increases the time required to measure an object, as well as increasing the possibility of error in the measurement.